E freyssinet



Sept. 12, 1939. E. FREYSSINET 2,172,703

METHOD OF CONSTRUCTING REINFORCED CONCRETE MONOLITHIC STRUCTURES FiledJan. 8, 1936 2 Sheets-Sheet l M941. 60 58 9 i6 %7 Q l m....v.v ...3 "J:f V a 0/ I "EL/ 111: ,4, fi/W 'fw 1 5y [j if, I z J m/m I"! E as t a. Nm W 46 In a I 1/ a INVE/ TOR Sept. 12, 1939. E. FREYSSINET 2,172,703

METHQD 0F CONSTRUCTING REINFORCED CONCRETE MONOLITHIC STRUCTURES FiledJan. 8, 1936 2 Sheets-Sheet 2 l/VVEA/ 7197 g 1 M71; f w

Patented Sept. 12, 1939 P AflENT OFFICE METHOD or coNs'rRUcrmGREINFORCED CONCRETE MONOLITHIC s'rauo'ruaes Eugene Freyssinet,Neuiliy-slir-Seine: France Application January 8, 1938, Serial No.58,183

In France January 11, 1935 8 Claims. (CL 25 -154 In my former patentsand publications, I have shown that'it is possible to considerablyincrease the qualities of reinforced concrete by employingreinforcements, made of steel having a high elastic limit, subjected topreliminary tensions sumciently high in order that they may remaintensioned so as to produce, in the concrete mass, systems of permanentstresses which advantageously modify those resulting from the efforts towhich the piece is subjected when in service. I thus obtain pieces whichhave exceptional qualities from the point of view of strength and cost.

These methods require the use of plants the weight, the cost, and thedifficulty of transportation and operation of which increase with thesize of the elements to be manufactured and which, for certain sizes,cannot be transported. Accordingly, the method above referred to washardly ever applied to the construction of mono 20f.

lithic structures up to the present time.

The method according to the present invention makes it possible to applythis method, which is based upon the provision of pre-stresses imposedto the materials, to reinforced concrete structures of any sizewhatever, having all the properties of monolithic structures made on thespot, by means of a plant which is little expensive and easy totransport and operate.

In order to build a structure with the method according to the presentinvention, I determine, as if I intended to make a monolithic structure,by applying the principles concerning the strength of materials, theshape and size of the structure and its reinforcements and the elasticstate that should be imparted thereto prior to the pouring of theconcrete that must embed said reinforcements, in order to obtain, priorto the setting of the concrete and to the various deformations thatsaidconcrete is to undergo, the system ofstresses that is most favorable tothe obtainment of-a strong finished construction.

This elastic state includes tensions, ranging between zero and theelastic limit of the metal,

to be applied either from one reinforcement to ings corresponding to thesurfaces of contact of.

ments extending through these intersurfaces.

These elements of the structureshall be' adjoining elements, hereinaftercalled intersurfaces.

These intersurfaces must be traced in such manner that, in the finishedstructure in service, the elastic efforts which shall be directed. atright angles thereto, shall always be compressive efforts, excepted inthe case of very small efforts. This can always be obtained by providinga suitable distribution of tensioned reinforce- Prior to pouring theconcrete of a first element,

the reinforcements that extend therethrough are placed, at least overthe length corresponding to said element, into the desired elasticstate, previously determined as above explained. I

In the most general case, this shall be obtained according to the UnitedStates patent applications, Ser. No. 395,297 filed September 26, 1929,

Ser. No. 714,724, filed March 8, 1934, Ser. No. 709,878. filed February5, 1934, Ser. No. 734,861 filed July 12. 1934, Ser. No. 734,863, filedJuly 12, 1934, by catching each reinforcement bar or group ofreinforcement bars by means of temporary anchorings consisting of clipsor the equivalent, subjected to' the action of jacks so as to elongatethe reinforcements, said jacks bearing upon members for the transmissionof efforts, generally disposed on the outside of the piece to bemanufactured.

After having waited for a sufficient hardening above explainedconcerning said first element;

For the reinforcements that are common to the first and second elements,it is necessary to 40 modify the intensity of the efforts that wereapplied, up to then, to these last mentioned reinforcements, bymodifying the conditions of working of the anchorings and jacks. As arule, this involves the creation of local efforts between thereinforcements and the concrete of the second element, and, furthermore,the application, to the whole of this element, of a force opposed to theresultant of the supplements of efforts applied to the variousreinforcements that extend therethrough. This involves the provision ofsuitable connection devices forming fixed abutments between thetensioning jacks or the like and the concrete of the first element.

Generally speaking, the local stresses thus im- In most industrialapplications, the necessity of allowing a considerable time to elapsebetween ithe moulding operations of an element and the operations ofadjusting the tensions prior to the moulding of the next element wouldrender the method useless. But it is known that the hardening ofconcrete can be accelerated through various operations the effects ofwhich can be amplified by associating them in a predetermined order, soas to permit of reducing the delays as much as it is necessary for theapplications that are considered. The favorable effect of. vibrationshas been known for a long time. I have found that, by associating in asuitable manner and under certain conditions a compression with thevibration, the results that are obtained are considerably improved, aswell from the point of view of the rapidity of hardening as from that ofthe final quality of the concrete. Concretes treated in this way can beheated without precautions or risks, even at temperatures higher than100 C., which permits of obtaining, in a period of time of less than twohours, with ordinary Portland normal concretes, resistances of severalhundreds of kilogrammes per square centi-v meter which, after finalhardening may exceed 1000 kgs. per sq. cm. It is thus possible to obtainthe desired hardening of the concrete in a very short time.

The method according to the present invention includes carrying out theoperations of moulding the successive elements in such manner thatconcrete is, in most cases, vibrated, compressed, and heated. Inexceptional cases, in which rapidity of working is not a very necessarycondition, heating, and even compression, may be dispensed with.

The general method above described affords, in all cases, a solution ofthe problem, but, in the. various specific cases that are met with, itis nearly always possible to simplify it, due to the fact that theparticular conditions of a given application generally permit thesimultaneous, or even conjugated, execution of operations which aredistinct a priori. In nearly all applications of the invention, theoperations of placing under tension, or increasing the tension of,certain reinforcements and compressing the concrete can, at leastpartly, be conjugated in such manner that one results from the other. Itsuffices, for this purpose, to maintain the walls of the mould againstthe pressure exerted by the concrete in. said mould, by connecting thereinforcements to these walls, which becomes particularly easy whenthese reinforcements normally extend through these walls and beyond them(case of the framing of an intersurface between two successiveelements). It is then possible, by making use of the resistance of thereinforcements for resisting a hydraulic thrust of the concrete,created'through any suitable means, to tension the reinforcements thustensioned, first temporarily through the hydraulic forces transmitted bythe compressed fresh concrete and the action of which shall befacilitated by maintaining an intensive vibration state therein, then,in a final manner, through the same concrete, once it has hardened. v

In both cases, the transmission of the efforts imposed to the firstelement by the action on these reinforcements needs not be made to thejacks through special connecting devices, which can therefore be whollyor partly dispensed with.

Another simplification may be effected whenever it is possible toincorporate a reinforcement in the first element without preliminarytension. {This permits of avoiding the necessity of a tempo- .raryanchoring for this reinforcement.

Generally speaking, any reinforcement has close to its end, a part inwhich there is no fatigue, or very little fatigue, which is notadvantageous to tension, and which forms an anchoring; thesimplification just above mentioned can therefore be applied frequently.It is even possible, in some cases to repeat it at both ends of areinforcement and thus to avoid the use of any system or metallic clamp.

The modification of the state of tension of the reinforcements betweenthe execution of two successive elements may correspond to only aportion of the reinforcements. It may also happen that a given state oftensioning is common to several successive elements. Of course, thismakes it possible to dispense with one or several operations ofadjusting the tensile stresses.

Several applications of the invention will be hereinafter described, butit should be well understood that they are merely intended to set forththe principles of the invention by showing their application to variousspecific cases. These examples are not in any way limitative. I

'Figs. 1 to 4 relate to the construction of a roof for a large span shedby means of beamsv having a vertical web and two treads.

Fig. 1 is a transverse sectional view of a moulding device for one ofthese beams, according to the invention;

Fig. 1' is an explanatory diagram;

Fig. 2 is a partial longitudinal section corresponding to Fig. 1; theconcrete filling the mould being broken away at various places to showthe internal parts of the mould;

Fig. 3 is a horizontal section on the line EDI-III of Fig. 1; y I

Fig. 4 is a diagrammatical view in vertical elevation of the whole of amoulding plant. according to the present invention.

Fig. i is a partial horizontal section on the line IV IV of Fig. 4,showing the fixation of the reinforcements to the base of the mould.

Figs. 5 and 6 are a sectional elevation of an abutment member, and .a.transverse section thereof, respectively;

Fig. 7 is a section of a device for engaging and holding a reinforcingrod.

The reinforcement system of the beam consists of a series ofhorizontalbars c, 0 0 ,0 grouped in the lower portion, uniformly distributedhorizontal bars u, and vertical bars 9', 1 All these bars might bemade'of steel,'for instance of a breaking strength of 100 kgs. per sq.mm. and of an elastic limit of 80 kgs. per sq. mm., obtained bypreliminary drawing. Furthermore,

the system includes reinforcements, made of steel of any grade whatever,disposed transversely to anchoring by a concrete hooplng eifect.The'reinforcements of hard steel shall be tensioned in such manner that,taking into account all the stresses imparted to the beam, as wellbending as shearing stresses, and all the deformations of the concrete(deformations due to shrinkage, elastic and plastic deformations) thereremains in the concrete, at any point, permanent compressions.

It is clear that. in this way, I eliminate any possibility of crackingof the beam.v It is then possible to have rates of shearing stresses ofthe same order of magnitude as the compression stresses, that is to saymuch higher than the mardmums usually accepted. On the other hand, themaximum compressive stresses are considerably lower than in ordinaryreinforced concrete. As a matter of fact, the diagram of these stresses(Fig. 1) is a line such as A 3 For ordinary reinforced concrete, thisdiagram would be a line A 3, in which 0 3 represents the deformation ofconcrete and 0A the deformation of steel.

In order to make the beam in question, I first determine, according tothe general method, the concrete elements to be successively poured. Inthis case, these elements may be divided into four groups:

1. elements embedding both portions of the reinforcements c of the samelength, close to their ends, and portions of the reinforcements a thatpenetrate thereinto (see for instance element l l-, Fig. 2);

2. elements embedding only portions'of reinforcements 7' close to theupper ends of these reinforcements (for instance elements 59, Fig. 2)

3. elements embedding only portions of reinforcements 7' close to theirlower ends;

4. elements limited by equidistant vertical planes PN-l, PN. etc. (Fig.3), constituting the whole of the remainder of the beam.

The concrete elements of the first group have decreasing widths in suchmanner as to leave a free passage for those of the reinforcements cwhich do not correspond thereto (see elements H, II, li in Fig. if).

I might, for the construction of the structure, apply the general methodabove set forth, but the work may be considerably simplified by notingthat the reinforcements extending through thefirst three groups ofelements or sections are not to be tensioned and that these elementshave no common surface. It is therefore possible to make themseparately, and even in advance, for those, for instance belonging togroups 2 and 3, the unitary volume of which is not too important andwhich can, therefore, be set in position after casting of the concrete.

It should also be noted that the reinforcements 0 common to all theelements of the fourth group through which they extend can be tensionedsimultaneously without any difficulty.

For this purpose, the=whole of the reinforcements is disposed on amember which forms the bottom of the mould for the whole beam. Thismember is constituted by a strong beam made of two elements a and acarrled by suitable frames such as 50 (Fig. 4) on'bases 5| which permitof placing them successively under each of the beams to be built.

The two beam elements a, a must be capable of being fixed or displacedvertically some centimeters by means of jacks 52 for permitting removalfrom the mould and they must be capable of having small movements in thedirection of their length, owing to the provision of rollers 53, underthe action ofjacks b which permit of movingtheir ends apart with a powerequal to the total maximum tension to be given to the whole of the mainreinforcements c, c c. p

This being done, the elements of the three first groups are poured andthe elements of the first group, such as l I (Fig. 2) are temporarilysecured to the bottom of the mould which-is for instance obtained bymeans of ridges l2 provided .on the upper face of said bottom and ofscrew spikes l3 extending into the moulded elements through the bottomof the mould (see also Figs. 4 and 4*) I may also employ abutmentmembers such as those shown in elevational view in Fig. 5 and intransverse section in Fig. 6. In these figures, I! designates a piece ofhigh resistance engaged through a hole provided in the bottom of moulderably engage an element II the removal of which, when the concrete ofthe piece moulded on bottom a has set and hardened, is intended tocreatean empty space which facilitates the separation from the mould.The whole is covered ments of the third group with the bottom of themould. Full hardening of the elements of the three first groups shall bemade as rapid as necessary by vibrating concrete or vibrating andcompressing it; or again by vibrating, compressing andheating it, forinstance by devising the ridges I 2 of the bottom of the mould,eventually screws It, in such manner that they can be heated through asteam circulation.

The two parts a. and a of the bottom of the or bars or recesses providedin the concrete surface of the mould, both in order to avoid that themass and rigidity of the mould bottoms may deaden the vibrations of theconcrete and in order to permit of said concrete being heated by steam,fiowing between metal sheet h and the mould bottom: Finally, thisarrangement facilitates the separation between the moulded concrete andthe niould.

I then set in position the framing of an element of the fourth group,said framing having the length of said element, which may be relativelysmall. This framing may be constituted as shown, by way of example,byFigs. 1 to 3. It includes sheet metal elements 1 F, l and sectionalelements m mflmf assembled together by longitudinal welds andconstituting tubular elements the lines of contact n of which areadjusted in such manner as to prevent the passage of solid material butto permit water to leak therethrough. These elements are assembled onsectional irons, o in such manner as after hardening of the concrete.

This mould being arranged in position, for instance in order to make theelement N of the fourth group at the end of the element Nl already made(Fig. 3), the vertical framing elements 54 separating it from the spacefor the next element N+i is set in position, the preceding element Nlclosing, on the other side, the end of the mould. These verticalframings 54 are fixed tothe horizontal reinforcements u, determined insuch manner that, at the desired rate of tension ofsaid reinforcements,they maintain said framing elements against the hydraulic pressure ofthe concrete, I may make use for this purpose, of device acting as stopsfor framings 54 and adapted to be fixed to the reinforcements (forinstance a system of wedges such as that shown at the upper part of Fig.3

and visible, on a larger scale, in Fig. '7; wedge 3 being blocked by ascrew 4, wedges 5 and 6, the apex angle of which is small, cannot bedisengaged and keep bar u in position, the unscrewing of screw 2releases the system).

The vertical framing elements 54 are provided with holes for the passageof the reinforcements and which may be fitted with packing members forpreventing leakage of concrete.

The upper part, or top, of the framing, which constitutes the lid of themould, is for instance made of U-shaped irons 55, arranged in transverseposition, welded to metal sheets 51 and upon which longitudinal I-shapedirons 58 are hearing. The whole is maintained by big screws 59a screwedin the elements 59. These screws are connected, for instance throughequalizing bars 591), with jacks 60 bearing upon I-shaped sectionalirons 58. Of course, when the parts are set in position for receivingconcrete, elements 59 are at a distance from bars 56, so as to permitrelative movement with respect thereto.

Orifices, provided for instance in the upper part of the framing, permitof filling the mould with concrete.

The concrete in the mould is vibrated for instance by means of shafts 52having unbalanced masses and revolving at high speed in bearings 63fixed to the lateral mould elements (Fig. 1).

After having filled the mould with concrete, the orifices for thisoperation are closed and jacks 60, which act upon the upper part of theframing, are operated. I may also act, by means of jacks or nuts, on therods p that connect together the two halves of the mould, on the rightand left side of the beam. It is clear that concrete is thus perfectlycompressed in all of its parts: The compression of concrete produces thetensioning of the vertical reinforcements j, 1' and of the horizontalreinforcements u throughmovable framing elements 51 and 54.

If it is desired to quickly remove the framing elements from theconcrete, steam is sent in contact with the concrete, by causing saidsteam to flow for instance through the channels of sectional irons m m mother channels for instance the hollow spaces existing between metalsheet h and the bottom of the mould, as above explained.

Once the element N of the beam has been made, the mould may be displacedtoward the' next element N+i through carriages rolling upon a tracksupported by the mould bottom a, a In the case of beams of variableheight, it shall suffice to add to or remove from the lateral moulds anelement of constant width. In a likewise manner, it is possible to varythe thickness of the webs or of the treads by merely changing therelative portions of the parts.

If the mould is of the same length as the ele-- and 55, or through mentto be moulded, the 'liquidtightness at the connection with the precedingelement NI precedingly moulded will be ensured by means of a deformableelement 65 which does not oppose the compression of the concrete. Thiselement 85 may consist of a metallic gutter provided with a rubberpacking member (Fig. 3).

The mould may be connected to the parts already moulded through suitableorgans such as 6| (Fig. 3) permitting deformations, these organs beingfixed to the concrete already hardened by making use of holes providedin the web, or of ridges 6| a moulded in the wall of the concrete pieceand against which the organs to be fixed are kept applied. It ispossible, in this case, to make use of the mould for tensioning thehorizontal reinforcements beyond what is possible when making use forthe pressure exerted by the concrete on the separation framing element54 of the successive concrete elements.

-It is possibleto make of pre-stressed concrete the portions of thestructure that connect to a beam the precedingly constructed beams,

For this purpose, it sumces to set in position, prior to pouring theconcrete of the beams, the reinforcements of these portions of thestructure that are at right angles to the-beams and penetrate thereinto..After the beams have been finished, these reinforcements shall easilybe tensionedby means of hydraulic jacks, suitably distributed, actingbetween the treads of the beams, and then concrete shall be poured.

It is unnecessary to prove the general character of the invention bygiving a great number of examples. Any structure, however complicated itmay be, can be obtained through the application of the general methodsabove described.

But it will be possible to find simplifications applicable to thevarious particular cases.

The invention is all the more advantageous as it is the case ofstructures subjected to stresses to which it is particularly difiicultto resist with ordinary methods of constructions, such as exceptionallyhigh fatigues, especially high shearing stresses or violently alternatedstresses.

The method according to the present invention is of course applicable toall kinds of structures, other than beams, for instance cylinders orprisms of any shape or dispositon, the method permitting the sinking, aswell as the construction of the structure, tubes and hollow or, solidcolumns for drilling, piles driven in any suitable manner, subterraneousor-submarine structures, such for instance as inverts, side-walls of acanal-lock, etc., which have to withstand high bending or shearingstresses and may have,'in length, width, and thickness, any dimensions,columns and pipes of any kind. The method is all the more advantageousas it permits of obtalning pieces the resistance of which tocompression, tension, bending stresses and torsion is enormous, the costof these pieces being very low due to the high resistance of theconcretes that are obtained and to the low cost of the hard steel wiresthat form the reinforcements.

Having thus fully described my invention, what I claim as new and desireto protect by Letters Patent is:

1. A method of making a monolithic structure .of reinforcedconcrete,which comprises, arrangto at least the portion of said reinforcementsthat corresponds to said element, pouring concrete into the spacelimited by said mould parts, allowing said concrete to set and harden,then arranging mould parts limiting one other element of the concretestructure, adjacent to the first mentioned one and impartingpredetermined tensions to at least the portion of the reinforcementsthat corresponds to said last mentioned element, pouring concrete intothe space corresponding to this last mentioned element, allowing thisconcrete to set and harden, and so on, until the whole structure isfinished, the tensions imparted to the reinforcements being always suchthat the mutual reactions of the respective elements thus formedsuccessively, over the surfaces along which they are assembled together,are essentially compressions tending to apply said elements against oneanother.

2. A method according to-claim 1 which further includes vibrating theconcrete of the successive elements so as to facilitate and acceleratethe hardening thereof.

3. A method according-to claim 1 which further includes vibrating andcompressing the concrete of the successive elements so as to improve andaccelerate the hardening thereof.

4. A method according to claim 1 which further includes vibrating,compressing and heating the concrete of the successive elements so as toimprove and accelerate the hardening thereof.

5. A method according to claim 1 which further comprises fixing at leastsome of the reinforcements extending through an element to one of thecorresponding mould parts, and compressing the concrete of said lastmentioned element by reducing the volume limited by said correspondingmould parts, whereby tensioning of said last mentioned reinforcements issimultaneously obtained.

6. A method according to claim 1 which further comprises fixing at leastsome of the reiniorcements extending through an element to one of thecorresponding mould parts, and compressing the concrete of said lastmentioned element by displacing another of said correponding mouldparts, whereby tensioning of said last mentioned reinforcements issimultaneusly obtained.

7. A method according to claim 1 which further comprises, providing amould part common to a plurality of concrete elements, securing hardenedconcrete elements, with reinforcements embedded therein, to said lastmentioned mould part, and tensioning said last mentioned reinforcementsbetween said last mentioned mould part and said last mentioned concreteelements.

8. A method according to claim 1 for the manufacture of a structureincluding a plurality of elements having reinforcements extendingthrough all these last mentioned elements and intended to be tensionedat the same rate over their whole length, which method furthercomprises, simultaneously tensioning the whole length of said lastmentioned reinforcements, prior to successively making these lastmentioned concrete elements.

EUGENE FREYSSINET.

